1. Field of the Invention
This invention relates to a flow sensor for detecting the flow quantity of a fluid.
2. Description of the Related Art
Previously, various flow sensors have been used for detecting the flow quantity of a fluid. For example, an ultrasonic vortex flow sensor ultrasonically detects a flow quantity change in a noncontact manner. A Karman vortex regularly occurs downstream from a vertex generation pole placed in a flow. The ultrasonic vortex flow sensor can ultrasonically detect a change in the Karman vortex, and can thereby detect the flow quantity with a high accuracy over a wide flow quantity range. (For example, refer to JP-A-4-77620 and JP-A-8-304142)
Such flow sensors include an integral-type flow sensor and a separate flow sensor. The integral-type flow sensor, which has a flow quantity detection part and a flow quantity display part in one piece, becomes larger. On the other hand, the separate flow sensor is provided in a detection section for detecting the flow quantity. A display section displays the value of the detected flow quantity. Generally, in the separate flow sensor, the detection section does not have a display section and thus can be miniaturized.
However, by installing the detection section, the user cannot check whether or not the flow quantity exists and whether or not the flow sensor processes normally.
FIG. 13 is an external perspective view of the detection section of the flow sensor in the related art, and FIG. 14 is an exploded perspective view of the detection section of the flow sensor in the related art.
As shown in FIG. 13, a detection section 900 has a casing 940 shaped like a rectangular parallelepiped and is provided with a through water pipe line 910 so as to pierce opposed sides of the casing 940. A circuit board 950 is placed above the through water pipe line 910.
As shown in FIG. 14, a cylindrical element storage part 920 is provided on both sides of the outer peripheral surface of the through water pipe line 910, and a transmitter 911 and a receiver 912 are inserted into the element storage parts 920. Each element storage part 920 is closed by a press member 930 having a convex part 9a in the central portion. Accordingly, the convex parts 9a of the press members 930 press the transmitter 911 and the receiver 912 against the outer peripheral surface of the through water pipe line 910. A taking-out pipe 970 of a conductor KB of the transmitter 911 and the receiver 912 of the through water pipe line 910 is provided in the direction crossing the element storage parts 920. Thus, the press members 930 each having the convex part 9a centrally press the transmitter 911 and the receiver 912 against the outer peripheral surface of the through water pipe line 910. In this case, the size of the detection section 900 of the flow sensor in the related art becomes larger in the direction in which the transmitter 911 and the receiver 912 are aligned. Also, the size of the detection section 900 of the flow sensor becomes larger in the direction crossing the direction in which the transmitter 911 and the receiver 912 are aligned. Since such a structure is housed in the casing 940, the detection section 900 is upsized as a whole. Recently, it has been desired to make the detection section 900 smaller.